Energy efficiency: 25-30 % of your heating/cooling bill comes from losses of energy through windows and doors. A 3’x5′ window with a 1/16″ gap around the sashes is equivalent to having a hole in the wall the size of a brick. Over the past 10 years windows and doors became much more energy efficient. New windows and doors will significantly reduce your energy bill. Air quality: Tight windows keep out dust, bugs, pollen and sound – so the indoor environment is healthier and more comfortable. Condensation: Energy-efficient windows stay warmer on the interior surface, so air humidity in winter can be raised to comfortable levels without getting windows to “sweat”, which if persistent may damage walls.